The relationship between control voltage and amplifier gain is an important performance measure of an variable gain amplifier (VGA). In this test, The amplifier is feed by the 8-bit DAC output of 16F1716 microcontroller, the micro is re-programmed each time to generate a different control voltage.
Input frequency=455KHz, Input power=-37dBm
The output level (RMS) is measured by oscilloscope and the relationship of control voltage and output level turns out like that.
On the other hand, let's compare to this, the datasheet figure of Analog Device AD603 Variable Gain Amplifier, the gain is very nicely linearly proportion to the control voltage. I don't know if this linearity is vital in radio IF amplifier application.
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